Mongodump of docker mongoDB instance to single timestamp named file - mongodb

Question

I'm doing backup dump of a mongoDb docker instance (mongo_db) via docker-compose (thanks to Matt for that snippet so far):
version: "3"
services:
mongo_db_backup:
image: 'mongo:3.4'
volumes:
- '/backup:/backup'
command: |
mongodump --host mongo_db --out /backup/ --db specific
Executing the command
$ docker-compose run mongo_db_backup
gives me all collections of specific db and stores them in /backup/specific.
Is it possible to get only one single (compressed) dump file, which is named as current time?
I'm using --out to get the files in the folder. The docs are saying I cannot use --archive together with --out.
Further more I need to use a env variable to set the archive output. Something like this:
mongo_db_backup:
image: 'mongo:3.4'
volumes:
- '/backup:/backup'
command:
- sh
- -c
- |
mongodump
--host mongo_db
--gzip
--db specific
$$(
if [ $TYPE = "hour" ]
then echo "--archive=/backup/hour/$$(date +"%H").gz"
elif [ $TYPE = "day" ]
then echo --archive=/backup/day/$$(date +"%d").gz
fi
)
Executing with $ docker-compose run -e TYPE=day mongo_db_backup

Answer 1

You can change your compose to below
version: "3"
services:
mongo_db_backup:
image: 'mongo:3.4'
volumes:
- '/backup:/backup'
command: sh -c "mongodump --host mongo_db --gzip --archive=/backup/$$(date +'%Y%m%d_%H%M%S') --db $${DB:=specific}"
Now if you want to change the DB you can run it like below
docker-compose run -e DB=abc mongo_db_backup
If you want to use it like docker-compose run mongo_db_backup abc then would need to create entrypoint.sh script handle the arguments in that. So it is easier to do it using environment variables
Edit-1 - Default behavior on missing environment variable
If you need to change the command based on environment variable being specified or not, you can change the command to below
command: sh -c "mongodump --host mongo_db --gzip --archive=/backup/$$(date +'%Y%m%d_%H%M%S') $$(if [ -z $DB ]; then echo '--db default_db'; else echo --collection $DB; fi)"
Edit-2: Multiline line command in compose with if else
To solve the issue of using multiline commands in compose you need to use a combination of array and multiline
command:
- sh
- -c
- |
multi line shell script
Below is the command I worked out for your update
command:
- bash
- -c
- |
TYPE=$${TYPE:=day}
if [ ! -d /backup/hour ]; then mkdir /backup/hour; fi
if [ ! -d /backup/day ]; then mkdir /backup/day; fi
mongodump --host mongo_db --gzip \
--db test \
$$( \
if [ "$$TYPE" == "hour" ]; then \
echo "--archive=/backup/hour/$$(date +'%H').gz"; \
elif [ "$$TYPE" == "day" ]; then \
echo "--archive=/backup/day/$$(date +'%d').gz"; \
fi \
)
Since docker-compose processes variables we need to escape each $ using $$. So $TYPE becomes $$TYPE. Also mongodump is a single command, so if you split it into multiple lines you need to use \ for multiline command continuation